Venous leg ulcer (VLU) is a common condition with substantial morbidity and a high cost in medical expenditures. Use of expensive innovative treatments, and evaluation of new therapies, is limited by the prolonged time period (24 weeks) required to assess the outcome (complete healing). A surrogate marker of complete wound healing is highly desirable in order to make clinical and therapeutic trials more efficient. Wound healing rate and percentage change in ulcer area are promising surrogate markers of complete wound healing based on previous small studies. The objective of this research project is to rigorously validate the candidate surrogate markers of complete wound healing in a large database through a series of retrospective cohort studies. The aims are: To validate the database diagnosis of VLU using a validity algorithm; to validate the candidate surrogate markers in a population of over 44,000 patients; and, to assess the impact of established risk factors for complete wound healing on the candidate surrogate markers using regression analysis. To develop the skills to perform these studies the investigator will pursue the Master of Science in Clinical Epidemiology (MSCE) degree program at the University of Pennsylvania. This research project will provide important data on the validity of novel markers for venous ulcer healing. Validation of these potential surrogate markers for wound healing will make future trials more efficient, potentially speed the discovery of new treatments, and allow clinicians to more rapidly determine if a patient is responding to a particular therapy. Through conducting these studies and pursuing the MSCE, the investigator will develop a series of epidemiological tools for which to apply to future scientific investigations.